We describe the implantation of a stent graft to seal off the left main coronary artery aneurysm of a 64-year-old man with guidance by intravascular ultrasound. The aneurysm was successfully sealed off. At 6-month and 1-year follow-up, a small residual aneurysm reappeared, which was treated conservatively. The technical issues in closing this aneurysm and the management of the residual aneurysm are discussed.